In highly polluted environments, salt spray corrosion is a key factor affecting the long-term reliability of epoxy resin cast dry-type transformers. Chloride ions in salt spray can penetrate the oxide film on metal surfaces, undergoing electrochemical reactions with the substrate, leading to corrosion of the casing, fasteners, and conductive components, and even causing a decline in insulation performance. Therefore, the casing sealing structure needs to be comprehensively designed through material selection, structural optimization, and protective processes to construct a multi-layered protection system to block the salt spray intrusion path and slow down the corrosion process.
The casing material must possess excellent resistance to salt spray aging. Traditional metal casings are susceptible to chloride ion corrosion, while using stainless steel or aluminum alloys can significantly improve corrosion resistance. Chromium in stainless steel can form a dense oxide film on the surface, effectively isolating salt spray; aluminum alloys can be anodized to generate a more corrosion-resistant alumina layer. For non-metallic casings, epoxy resin composites are an ideal choice due to their low water absorption and high chemical stability, especially glass fiber reinforced epoxy resin castings, which can maintain structural strength while preventing embrittlement or cracking caused by salt spray penetration.
The core of the sealing structure design lies in minimizing gaps and pores. The joints of the outer casing must be designed without gaps, for example, by using precision molding in one piece or laser welding to eliminate weld seams and prevent salt spray from accumulating in tiny gaps. For interfaces that must be retained (such as ventilation windows and cable entry/exit points), a double sealing device is required: an outer layer uses a dustproof mesh to intercept large salt particles, and an inner layer uses a silicone rubber sealing ring or epoxy resin potting compound to fill the gaps, forming a physical barrier. In addition, a drainage channel can be designed at the bottom of the casing to guide condensate or seeping salt solution out, preventing liquid accumulation from accelerating corrosion.
Protective coatings are a key means of improving the salt spray resistance of the casing. Composite coating systems typically consist of a primer, intermediate coat, and topcoat: the primer uses a zinc-rich coating to protect the substrate through the sacrificial anode effect of zinc; the intermediate coat uses epoxy micaceous iron oxide paint to enhance coating thickness and impermeability; and the topcoat uses fluorocarbon paint or polyurethane paint, which has strong weather resistance and can maintain gloss and adhesion in salt spray environments for a long time. Coating application requires strict environmental control, ensuring a dust-free environment and low-temperature drying to prevent the formation of pores or pinholes within the coating. Otherwise, salt spray can penetrate these defects directly to the substrate.
Structural sealing also needs to consider environmental adaptability. For example, in coastal or high-humidity areas, the epoxy resin cast dry-type transformer housing may face the dual challenges of salt spray and condensation. In such cases, an integrated temperature control system is necessary, using heaters or air conditioning to regulate internal humidity and prevent condensation from forming conductive pathways. Simultaneously, a hydrophobic coating can be sprayed onto the housing surface to reduce the adhesion of salt solutions and decrease the risk of chloride ion penetration. For vibration environments (such as offshore wind power platforms), elastic sealing materials (such as silicone) should be used instead of rigid seals to absorb vibration energy and prevent seal fatigue failure.
Maintenance strategies are crucial for the long-term effectiveness of the sealing structure. Regularly clean salt crystals from the housing surface to prevent chloride ion accumulation; check the aging of sealing strips and replace cracked or deformed components promptly; monitor insulation resistance and winding temperature rise to detect insulation degradation caused by corrosion early. Furthermore, a smart monitoring interface can be reserved to transmit housing sealing status data in real time, providing a basis for preventative maintenance. The casing sealing structure design of epoxy resin cast dry-type transformers must adhere to the principle of "prevention first, combined with protection." This involves a comprehensive approach, including material upgrades, structural optimization, coating protection, and intelligent maintenance, to construct a multi-layered protection system from the outside in. This not only effectively resists salt spray corrosion and extends the service life of the epoxy resin cast dry-type transformer, but also reduces total life-cycle maintenance costs, providing reliable assurance for the safe operation of power equipment in highly polluted environments.
